Islamabad: Thousands of Pakistanis flocked to a school in the northwestern city of Peshawar on Sunday to mourn the 149 people -- mainly children -- massacred by the Taliban and demand action against militants.

Men, women and children from Peshawar and other cities visited the army-run institution to offer prayers for those killed in the country`s deadliest-ever terror attack.

Pakistan has described Tuesday`s bloody rampage as its own "mini 9/11", calling it a game-changer in the fight against extremism.

Mourners placed flowers, bouquets, placards and lighted candles at various places in the school in front of photos of murdered students.

Masons laid bricks and poured cement to raise the height of the wall around the Army Public School as mourners chanted slogans such as "Death to terrorists", "Long live Pakistan army", "The blood of martyrs will not go waste" and "Taliban are savages".

"What kind of a person can kill a child?" asked local resident Imdad Hussain, who came to pray for the children.

"What kind of justice is this, what kind of Islam is this?" he asked, urging the government swiftly to wipe out terrorists.

A local woman who had covered her face with a shawl said parents had thought their sons and daughters would be safe in school. But now they believed their children were not safe anywhere.

"First they attacked mosques, then markets and now they have started attacking schools. We cannot tolerate this. We can die, but we will not let our children be killed," she said.

Shugufta Bibi, 28, told AFP her friend lost his son in Tuesday`s attack and she had come to pay respects to his memory.

"I demand that the government close in on the terrorists and hang them in public," Bibi said.

Tributes and condolences poured in on social media websites Facebook and Twitter.

After the attack Prime Minister Nawaz Sharif ended a six-year moratorium on the death penalty, reinstating its use for terrorism-related cases.

Two militants convicted of separate offences were the first to face the noose.

Human Rights Watch termed the executions "a craven politicised reaction to the Peshawar killings" and demanded that no further hangings be carried out.

The two militants hanged Friday in the central province of Punjab were Aqil, convicted of an attack on army headquarters in Rawalpindi in 2009, and Arshad Mehmood -- sentenced for involvement in a 2003 assassination attempt on then-military ruler General Pervez Musharraf.

Pakistan put all its airports on red alert Saturday as the military intensified operations against militants in the lawless northwestern tribal areas.

The Taliban said the school attack by a suicide squad was revenge for the killing of militants` families in that offensive.

The military has since June been waging the assault against longstanding Taliban and other militant strongholds.

But a series of fresh strikes since the Peshawar attack, in which dozens of alleged militants were killed, suggest the campaign is being stepped up.

The army has also been deployed to guard major prisons housing militants. Officials have said there would be up to ten more executions in coming days.

Several educational institutions, including the prestigious Quaid-e-Azam University in Islamabad, have been shut indefinitely, citing security threats.